Novak Djokovic revealed he was "right at the limit" of his physical and mental endurance in "brutal" Melbourne temperatures following a win over Gael Monfils, who said he was "dying on court for 40 minutes."

It was almost 40 degrees Celsius when Djokovic and Monfils were doing battle on Rod Laver Arena, so dropped to around 30°C by the time Federer defeated Struff 6-4 6-4 7-6 (7-4).

The defending champion revealed that he asked to play at night, but there were no guarantees that he would be granted his wish.

"There are maybe 60 guys asking for stuff and I am one of those guys, yes," said the 19-time grand slam champion.

"Possibly [I have more leverage] but it is not my call it is their call. There are guys like Novak, other guys who they're going to listen to of course, the Aussies. TV as well,

"I am happy I didn't have to go from night to day and back to night, so I was happy to stay in the same rhythm. I wouldn't have minded playing during the day.

"I hope I survive under those conditions too because if you want to get to the top you have to play in all sorts of conditions. It is more helpful to play now than in the day."

Federer, who will play Richard Gasquet in round three, reflected on another job well done after his second straight-sets victory of the week.

"I'm happy I'm still part of [the tournament] really, because I knew Struff could be tough today." said the second seed.

"If you look at the last two matches that I've played, I felt like both of my opponents [he beat Aljaz Bedene on Tuesday] pretty much kind of went for broke. When they see a mini chance to get on the offensive, they just go for it.

"You don't want to be in defence too much. The moment you see an opening, you go for it."